Typically, a sensor measures a certain physical quantity and generates a corresponding sensor data signal, which is transmitted from a data transmission unit of the sensor assembly to the receiver, and there, an application unit allocated to the receiver of the sensor data signal is controlled dependent thereon. If, in addition to the sensor data signal, further data, be they control signals for controlling the data transmission or additional or auxiliary data, are to be transmitted, then a different value range of the data signal can be used for this purpose, thus, for example, a higher amplitude for analog signals, or a reserved bit value range for digital signals. As an alternative thereto, there is a possibility of a multiplex operation, in which the value range of the sensor data signal can be used for the additional data signal. In all cases, however, in addition to the sensor assembly as a transmitter, respectively also all of the receivers must recognize this data transmission protocol or the respective type of operation. Especially in sensor data bus systems, in which a plurality of sensor assemblies and receivers are connected together on a bus, therefore an adaptation of all bus participants is necessary, even if such additional data are to be exchanged between only a few participants. A utilization of assemblies of an older generation, i.e. a downward compatibility, is thus excluded. Otherwise, error functions or malfunctions could arise in the receiver or in the application unit, with respect to receivers which do not recognize that the transmitted data are additional data signals.
Such sensor data bus systems are, for example, used in motor vehicles for the acquisition of safety relevant sensor data signals for the controlled activation of occupant protection devices.
In this context, for example, if additional data signals would be transmitted instead of acceleration data signals, and a receiver of an occupant protection device would not recognize this, either because it just did not receive a corresponding control signal due to an interference, or because it is not at all prepared for such a transmission of additional data signals, then there exists the danger of the erroneous triggering of the occupant protection device.